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2 Decay of 150 Nd, Preliminary Results (PhaseI data). Nasim Fatemi-Ghomi. Introduction. Background study of 150 Nd 2 A study of the 207 Bi and 214 Bi background in the e -channel. A study of the 210 Bi, 207 Tl+ 211 Pb and 234m Pa background in the e-channel. - PowerPoint PPT Presentation
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Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
2 Decay of 150Nd, Preliminary Results
(PhaseI data)
Nasim Fatemi-Ghomi
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
Introduction
Background study of 150Nd2• A study of the 207Bi and 214Bi background in the e-channel.• A study of the 210Bi, 207Tl+211Pb and 234mPa background in the e-channel.• Cross check external background with Cu foil.
Extraction of half-life of 150Nd2
Data Selection
• Good betbeta runs between 2019-3395 (phase I).• Data taking time =2.8836 x 107s = 0.91 yrs.• Events should come from Nd2O3. The foil has 57g mass (37gr pure 150Nd).
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
Internal BackgroundInternal Background
Bg Act(mBq/kg) Ge measurement
Modane-Baksan
Found from 1e channel slide 8
210Bi 368.42 -
207Tl 163.0 -
211Pb 163.0 -
234mPa 84.4 -
Found from eChannel slide 6
207Bi 235 128 - 120
Fround from e + Slide 7
214Bi 15.3 < 3 - 20
V.Tretyak(Aussois 2005)
40K 66.7 < 6.6 - 9.6
V.Vasiliev (Dubna 2004)
208Tl 7.95 9.6 - 5
228Ac 22.1 20 - 15
212Bi 22.1 -
Ge measurement
152Eu 38.3(modane) 21.6(Baksan)
External Background &External Background & Background on the SurfaceBackground on the Surface of the Wires and Foils.of the Wires and Foils.
Bg Act(Bq)
SW 214Bi 0.623
SW 214Pb 0.623
SF 214Bi 0.0185
SF 214Pb 0.0185
PM 214Bi 374
PM 214Pb 374
PM 228Ac 515
PM 60Co 50.7
PM 40K 954
Air 214Pb 702
Air 214Bi 702
Found byFound byV.Vasilev V.Vasilev checkedcheckedwith Cu foilwith Cu foilSlide 9Slide 9
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
207Bi and 214Bi Background Studies
Pre-Selection Cuts for e-channel:• One negatively charged track associated with an isolated PMT (E(e)> 0.2MeV).• Only one cluster with E()> 0.2MeV. No other with E()> 0.15MeV.• Internal TOF hypothesis for e events > 5% & external hypothesis < 1%.• Tracks must have one hit in one of the two first layers of GG.
Cos(e) < 0.9
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
Fit Fit 207207Bi with the data minus backgroundBi with the data minus background
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Activity ofActivity of 207 207BiBi
In addtion to the pre-selection criteria described there should not be any single or In addtion to the pre-selection criteria described there should not be any single or group delayed hit(s) in the tracker. group delayed hit(s) in the tracker.
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
Look at the energy region 0.7 MeV< Ee <1.1 MeV and 0.25 MeV< ELook at the energy region 0.7 MeV< Ee <1.1 MeV and 0.25 MeV< E <0.6 MeV <0.6 MeV where where 207207Bi dominated over all other backgrounds.Bi dominated over all other backgrounds.
AA207Bi207Bi=13.4 ± 0.3 mBq ~ 235 ± 5 mBq/kg =13.4 ± 0.3 mBq ~ 235 ± 5 mBq/kg
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Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
Activity of Activity of 214214Bi Bi
Events should accompany with an alpha particle (delayed or single hits.) Events should accompany with an alpha particle (delayed or single hits.)
AA214Bi 214Bi = 0.87 = 0.87 0.17 mBq ~ 15.26 0.17 mBq ~ 15.26 2.98 mBq/kg 2.98 mBq/kg
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Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
1e Channel1e Channel
Selection cuts:Selection cuts:• One track with negative charge associated with isolated PMT.One track with negative charge associated with isolated PMT.• Track has to have a reconstructed vertex.Track has to have a reconstructed vertex.• E(e) > 0.5 MeV. E(e) > 0.5 MeV. • Track has to have a hit in one of the first two layers of GG.Track has to have a hit in one of the first two layers of GG.
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mBq
210Bi 21.0 0.3 0.3
207Tl 9.29 0.15 0.15
211Pb 9.29 0.15 0.15
234mPa 4.81 0.050.05
Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
External backgroundExternal background
The external background activity found by V.Vasiliev is checked with The external background activity found by V.Vasiliev is checked with looking at the energy distribution of the energy of e- looking at the energy distribution of the energy of e- events coming from events coming from the Cu foil. the Cu foil.
Data = 35524±188, Total Background=34251± 382Data = 35524±188, Total Background=34251± 382Data-Background= 1273 ± 425 -> has to be added to the Data-Background= 1273 ± 425 -> has to be added to the systematic uncertainty.systematic uncertainty.
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Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
150150Nd Half-lifeNd Half-life
Pre-selection for Pre-selection for 150150Nd to 2Nd to 2 events: events:• Two negatively charged tracks associated with isolated PMTs and E1 ,E2 > 0.2 MeV.• Both electrons originate from a common vertex with |∆r| < 2 cm & |∆z| < 4 cm.• Internal TOF hypothesis > 4% & external TOF hypothesis < 1%.• Track starts from layers 1 & 2 of GG.• No delayed alpha decay with refiring time > 70 s.• No single or group delayed hit(s).
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Nasim Fatemi-Ghomi, Dubna meeting 17-20 September 2006
ResultsResults
Number of data events: 1011
Number of total background: 315
Efficiency =133643/2000000 6.68%
T12= (9.04 -0.57+0.63(stat) +- 0.40 (Act)+- 0.78 (syst)) x 1018 y